Association between the systemic immune-inflammation index and the efficacy of neoadjuvant chemotherapy, prognosis in HER2 positive breast cancer—a retrospective cohort study

BACKGROUND: The prognosis of patients who can achieve a complete response after neoadjuvant chemotherapy could be significantly improved. Thus, accurately predicting the efficacy of neoadjuvant chemotherapy is of great clinical significance. Currently, previous indicators such as neutrophil to lymphocyte ratio was poor in predicting the efficacy and prognosis of neoadjuvant chemotherapy in human epidermal growth factor receptor 2 (HER2) positive breast cancer patients. METHODS: The data of 172 HER2 positive breast cancer patients admitted to the Nuclear 215 Hospital of Shaanxi Province from January 2015 to January 2017 were retrospectively collected. After neoadjuvant chemotherapy, the patients were divided into the complete response group (n=70) and the non-complete response group (n=102). The clinical characteristics and systemic immune-inflammation index (SII) levels of the two groups were compared. The patients were followed-up for 5 years post-surgery to observe whether recurrence or metastasis occurred after the operation by clinic visit combined with telephone calls. RESULTS: The SII of the complete response group was significantly lower than that of the non-complete response group (587.43±175.97 vs. 821.82±231.58; P=0.000). The SII was valuable in predicting which HER2 positive breast cancer patients would fail to achieve a pathological complete response, and the area under the curve (AUC) was 0.773 [95% confidence interval (CI): 0.705–0.804; P=0.000]. A SII >755.10 was an adverse factor for HER2 positive breast cancer patients achieving a pathological complete response after neoadjuvant chemotherapy [P=0.000; relative risk (RR): 0.172 (95% CI: 0.082–0.358)]. The SII level was valuable in predicting recurrence within 5 years of surgery, and had an AUC of 0.828 (95% CI: 0.757–0.900; P=0.000). A SII >755.10 was a risk factor for recurrence within 5 years of surgery [P=0.001; RR: 4.945 (95% CI: 1.949–12.544)]. The SII level was valuable in predicting metastasis within 5 years of surgery, and had an AUC of 0.837 (95% CI: 0.756–0.917; P=0.000). A SII >755.10 was a risk factor for metastasis within 5 years of surgery [P=0.014, RR: 4.553 (95% CI: 1.362–15.220)]. CONCLUSIONS: The SII was associated with the prognosis and efficacy of neoadjuvant chemotherapy in HER2 positive breast cancer patients.